1. Technical Field of the Invention
The present invention relates to a technique for adjusting focus offsets in an optical disc apparatus which records information on or reproduces information from an optical disc having a plurality of recording layers.
2. Description of the Related Art
Conventional techniques related to the present invention and intended to set and adjust focus offsets for the plural recording layers of an optical disc are described in, for example, Japanese Patent Specification (JP Spec.) No. 3465413 and Japanese Patent Laid-Open (Kokai) No. 2003-217140. The technique disclosed in JP Spec. No. 3465413 is as described below. First, a change of a recording layer is followed by the calculation of the difference between either the maximum tracking error signal amplitude values, maximum RF signal amplitude values, or minimum reproduction signal jitter levels measured before and after the change. If the difference is smaller than a required value, the value obtained before the change was used as the optimum value, or if the difference is larger than the required value, means for generating offsets is controlled and the optimum point is detected. The technique disclosed in Japanese Patent Laid-Open No. 2003-217140 is as described below. Offsets are controlled to obtain the maximum RF signal developed at the pre-pits that have been recorded in the grooves and lands of various recording layers, and independent focus offsets are set for each recording layer.
However, since the above conventional techniques both assume that information is already recorded in each recording layer (recording layer), it is considered to be difficult to set focus offsets for recording layers not having any information recorded thereon.
In order to solve this problem, according to the present invention allowing for the status of the above conventional techniques, appropriate focus offsets in an optical disc apparatus can be set, even for an unrecorded recording layer (a recording layer without recorded information).
An object of the present invention is to provide a technique that allows resolution of the problem involved and improvement of an optical disc apparatus in operational convenience.